(1) Field of the Invention
The present invention relates to the manufacture of membrane keyboard. Specifically, the present invention relates to a keyboard including spatially separated keys and having a construction which will simulate or give the effect of long travel (on the order of 0.100" or more) as compared to a short travel (about 0.003"-0.010") of a conventional membrane keyboard. Accordingly, the general objects of the present invention are to provide novel and improved methods and apparatus of such character.
(2) Description of the Prior Art
Early prior art flat membrane keyboards failed to provide a user with any indication that the key had been activated because of the very limited movement of the keys. This demonstrated the desirability of providing membrane keyboards with keys capable of providing the user with a sensation of movement to indicate key activation. More recent prior art membrane-type keyboards incorporating a snap-action element to provide sensation of movement through tactile feedback, have a flat flexible legend sheet defining the area which the user must depress to actuate the snap-action element associated with that particular area.
The disadvantages associated with this prior art are the additional expense of producing the circuit board with the snap-action element and the fact that the user must visually locate the key area on the flat flexible legend before the key is depressed. Further, in many devices, if the user depressed the key at a point removed from the center of the key, the electrical circuit contacts operated by the key may be closed without providing the sensation of movement or the key may provide the movement sensation without contact being made. The accuracy of the data entered by means of the keyboard accordingly, is a function of the operator's attentiveness.
The prior art discloses various methods of alleviating the above-mentioned problems associated with locating the keys visually on the flat flexible legend. One such method involves providing the flexible legend with indentations which are aligned with the snap-action elements of the circuit board. Because of these indentations the flexible sheet must be separated from the circuit board by a compressionable medium. While overcoming the above mentioned disadvantages associated with visually locating keys, this method requires additional expense in manufacturing the keyboard.
Some of the objects of the present invention are to provide an improved membrane keyboard wherein the keys may be located by a user nonvisually and also to provide the user with a sensation of movement.